The talented young prop will remain at Emerald Headingley until at least the end of the 2022 season.
Polish-born Oledzki made his debut last year and cemented his place in the first-team squad with 22 appearances.
It was no surprise he earned a Knights call-up and he represented them in Papua New Guinea this autumn.
Oledzki, 20, said: “It means a lot to me that Kevin Sinfield, Gary Hetherington, Dave Furner and our staff have faith in me and what I can achieve.
“I want to return that belief by playing my best rugby in the years ahead. It’s great to have my new contract all sorted. My first was a five-year deal and this is another long-term commitment from the club to me and vice versa.
“I have signed as I believe Leeds is one of the greatest clubs in the world and I want to play here.
“I am looking forward to the new season and trying to help the side win some silverware.”
The front-row is relishing working under new head coach Furner, the ex-Kangaroos international who was one of the toughest forwards around during his illustrious playing career.
Oledzki said: “He’s introduced a lot of fresh aspects to our training, which the younger players in particular are really thriving on.
“We know we have a clean slate and he’s going to give us a chance, but it’s down to us to make the most of that opportunity.
“Every player wants to achieve big things and take Leeds back to where we think we belong.”
Director of rugby Sinfield commented: “I’m delighted Mikolaj has agreed a new long-term contract.
“He has worked incredibly hard over the last few years to develop his game, but he’d be the first to admit there’s still plenty he can work on over the coming years.
“He’s one of the most enthusiastic members of our squad and earned his place in the England Knights squad through his performances last year.”